The .beta.-lactam halide compound represented by the general formula (2) is prepared by reacting halogen molecules with an allenyl .beta.-lactam compound represented by the general formula (1) below as is already known (Can. J. Chem., 1978, 56, 1335). However, this process affords a mixture of .alpha., .beta.-lactam and .beta., .gamma.-position isomers depending on the kind of halogen molecule and is not usable in actuality. It is also reported that as shown in the diagram, a keto-form .beta.-lactam compound is enolized into an enol ether or vinyl halide, followed by halogenation with N-bromosuccinimide or N-chlorosuccinimide in the presence of a radical generating agent (JP-A-135859/1983). Since this process requires use of a hazardous reagent for reaction, processes which are industrially more feasible are desired ##STR3## wherein the group A, group S--D and group E are groups analogous respectively to the group R.sup.1 /R.sup.2, group R.sup.4 and group R.sup.3 of the invention to be described below.
An object of the present invention is to provide a process for preparing a .beta.-lactam halide compound represented by the general formula (2) through a simple procedure in a high yield with a high purity using an allenyl .beta.-lactam compound represented by the general formula (1) as the starting material, by developing a novel halogenating reagent having a high position selectivity.